Polymeric compositions

ABSTRACT

An aqueous composition suitable for use, when dry, as an improved elastomeric coating, caulk, sealant, or pressure sensitive adhesive is provided including a predominantly acrylic aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from −90° C. to 20° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weight based on the total weight of said polymer, ethylenically unsaturated carboxylic acid monomer until 90-99.7% of said monomers by weight, based on the total weight of said polymer, has been converted to polymer and subsequently at least half of the remaining monomer is converted to polymer in the presence of 0.1-1.0 wt %, by weight based on the total weight of said polymer, t-amyl hydroperoxide. A method for preparing the emulsion polymer, a method for coating a substrate to provide an elastomeric coating on a substrate, a method for applying an aqueous caulk or sealant composition to a substrate, and a method for providing a pressure sensitive adhesive on a substrate are also provided.

[0001] This invention relates to an aqueous composition suitable for usewhen dry as an improved elastomeric coating, caulk, sealant or pressuresensitive adhesive, a method for preparing an aqueous emulsion polymersuitable for use as an improved elastomeric coating, caulk, sealant orpressure sensitive adhesive, and a methods for providing an improvedelastomeric coating, caulk or sealant, or pressure sensitive adhesive.More particularly this invention relates to an aqueous compositionsuitable for use when dry as an improved elastomeric coating, caulk,sealant or pressure sensitive adhesive including a predominantly acrylicaqueous emulsion polymer, the polymer having a glass transitiontemperature (Tg) from −90° C. to 20° C., the polymer formed by the freeradical polymerization of at least one ethylenically unsaturatednonionic acrylic monomer and 0.5-5%, by weight based on the total weightof the polymer, ethylenically unsaturated carboxylic acid monomer, until90-99.7% of the monomers by weight, based on the total weight of thepolymer, has been converted to polymer; and the subsequentpolymerization at least half, by weight, of the remaining monomer topolymer in the presence of 0.1-1.0%, by weight based on the total weightof the polymer, t-amyl hydroperoxide.

[0002] The present invention serves to provide an aqueous compositionsuitable for use when dry as an improved elastomeric coating, caulk, orsealant so as to retain its integrity without cracking under stress evenat temperatures below 0 C. Elastomeric coatings, caulks, and sealantsare frequently applied to buildings and othe constructions subjected tooutdoor temperature extremes and desirably retain their integrity undersuch conditions. Also, the present serves to provide an aqueouscomposition suitable for use when dry as an improved pressure sensitiveadhesive having improved tack which may be desirable in itself or,alternatively, provide the basis for ehancement of other adhesiveproperties such as peel or shear strength with retention of usefullevels of tack.

[0003] U.S. Pat. No. 5,540,987 discloses emulsion polymers having lowresidual formaldehyde and providing saturated cellulosic webs havingimproved tensile strength. The polymers are formed by the use of anhydrophobic hydroperoxide and ascorbic acid initiator throughout thecourse of the reaction.

[0004] The problem faced by the inventors is the provision of an aqueouscomposition suitable for use when dry as an improved elastomericcoating, caulk, sealant or pressure sensitive adhesive. Unexpectedly,the inventors found that the use of t-amyl hydroperoxide in the laststages of the polymerization was sufficient to provide polymers whichled improved elastomeric coating, caulk, sealant or pressure sensitiveadhesives.

[0005] In a first aspect of the present invention there is provided anaqueous composition suitable for use when dry as an improved elastomericcoating, caulk, sealant or pressure sensitive adhesive including apredominantly acrylic aqueous emulsion polymer, the polymer having aglass transition temperature (Tg) from −90° C. to 20° C., formed by thefree radical polymerization of at least one ethylenically unsaturatednonionic acrylic monomer and 0.5-5%, by weight based on the total weightof the polymer, ethylenically unsaturated carboxylic acid monomer until90-99.7% of the monomers by weight, based on the total weight of thepolymer, has been converted to polymer and subsequently at least half ofthe remaining monomer is converted to polymer in the presence of0.1-1.0%, by weight based on the total weight of the polymer, t-amylhydroperoxide.

[0006] In a second aspect of the present invention there is provided amethod for preparing an aqueous emulsion polymer suitable for use in animproved elastomeric coating, caulk, sealant or pressure sensitiveadhesive including forming a predominantly acrylic aqueous emulsionpolymer, the polymer having a glass transition temperature (Tg) from−90° C. to 20° C., by the free radical polymerization of at least oneethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weightbased on the total weight of the polymer, ethylenically unsaturatedcarboxylic acid monomer until 90-99.7% of the monomers by weight, basedon the total weight of the polymer, has been converted to polymer; andsubsequently polymerizing at least half of the remaining monomer topolymer in the presence of 0.1-1.0%, by weight based on the total weightof said polymer, t-amyl hydroperoxide.

[0007] In a third aspect of the present invention there is provided amethod for coating a substrate with an aqueous composition to provide anelastomeric coating on a substrate. In a fourth aspect of the presentinvention there is provided a method for applying an aqueous caulk orsealant composition to a substrate. In a fifth aspect of the presentinvention there is provided a method for providing a pressure sensitiveadhesive on a substrate.

[0008] This invention relates to an aqueous composition suitable for usewhen dry as an elastomeric coating having improved low temperatureelongation including a predominantly acrylic aqueous emulsion polymer,the polymer having a glass transition temperature (Tg) from −90° C. to20° C., formed by the free radical polymerization of at least oneethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weightbased on the total weight of the polymer, ethylenically unsaturatedcarboxylic acid monomer until 90-99.7% of the monomers by weight, basedon the total weight of the polymer, has been converted to polymer andsubsequently at least half of the remaining monomer is converted topolymer in the presence of 0.1-1.0%, by weight based on the total weightof the polymer, t-amyl hydroperoxide.

[0009] The predominantly acrylic aqueous emulsion polymer contains atleast one copolymerized ethylenically unsaturated nonionic acrylicmonomer. By “predominantly acrylic” herein is meant that the polymercontains greater than 50%, by weight, copolymerized units deriving from(meth)acrylic monomers such as, for example, (meth)acrylate esters,(meth)acrylamides, (meth)acrylonitrile, and (meth)acrylic acid. The useof the term “(meth)” followed by another term such as acrylate oracrylamide, as used throughout the disclosure, refers to both acrylatesor acrylamides and methacrylates and methacrylamides, respectively. By“nonionic monomer” herein is meant that the copolymerized monomerresidue does not bear an ionic charge between pH=1-14.

[0010] The ethylenically unsaturated nonionic acrylic monomers include,for example, (meth)acrylic ester monomers including methyl acrylate,ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate,lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecylmethacrylate, lauryl methacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate. Other ethylenically unsaturated nonionicmonomers which may be incorporated into the polymer with the provisothat the polymer must be predominantly acrylic in composition include,for example, styrene and substituted styrenes; butadiene; vinyl acetate,vinyl butyrate and other vinyl esters; and vinyl monomers such as vinylchloride, vinylidene chloride. Preferred are all-acrylic,styrene/acrylic, and vinyl acertate/acrylic polymers.

[0011] The emulsion polymer contains from 0.5% to 5%, by weight based ontotal monomer weight, of a copolymerized monoethylenically-unsaturatedcarboxylic acid monomer, based on the weight of the polymer, such as,for example, acrylic acid, methacrylic acid, crotonic acid, itaconicacid, fumaric acid, maleic acid, monomethyl itaconate, monomethylfumarate, monobutyl fumarate, and maleic anhydride.

[0012] The emulsion polymer used in this invention may contain from 0%to 1%, by weight based on monomer weight, copolymerizedmulti-ethylenically unsaturated monomers such as, for example, allylmethacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate,1,2-ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, anddivinyl benzene.

[0013] The glass transition temperature (“Tg” ) of the emulsion polymeris from −90° C. to 20° C., as measured by differential scanningcalorimetry (DSC) taking the mid-point in the heat flow versustemperature transition as the Tg value, the monomers and amounts of themonomers being selected to achieve the desired polymer Tg range as iswell known in the art. Preferred Tg of the emulsion polymer forelastomeric wall coatings is from −40 ° C. to 20° C.; of caulks andsealants is −60° C. to 20° C.; of pressure sensitive adhesives is −90°C. to 0° C.

[0014] The polymerization techniques used to prepare aqueousemulsion-polymers are well known in the art. In the emulsionpolymerization process conventional surfactants may be used such as, forexample, anionic and/or nonionic emulsifiers such as, for example,alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates,sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts;fatty acids; ethylenically unsaturated surfactant monomers; andethoxylated alcohols or phenols. The amount of surfactant used isusually 0.1% to 6% by weight, based on the weight of monomer. Eitherthermal or redox initiation processes may be used. The reactiontemperature is maintained at a temperature lower than 100° C. throughoutthe course of the reaction. Preferred is a reaction temperature between30° C. and 95° C., more preferably between 50° C. and 90° C. The monomermixture may be added neat or as an emulsion in water. The monomermixture may be added in one or more additions or continuously, linearlyor not, over the reaction period, or combinations thereof.

[0015] Conventional free radical initiators may be used such as, forexample, hydrogen peroxide, sodium peroxide, potassium peroxide, t-butylhydroperoxide, cumene hydroperoxide, ammonium and/or alkali metalpersulfates, sodium perborate, perphosphoric acid and salts thereof,potassium permanganate, and ammonium or alkali metal salts ofperoxydisulfuric acid, typically at a level of 0.01% to 3.0% by weight,based on the weight of total monomer. Redox systems using the sameinitiators coupled with a suitable reductant such as, for example,sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkalimetal and ammonium salts of sulfur-containing acids, such as sodiumsulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrosulfide ordithionite, formadinesulfinic acid, hydroxymethanesulfonic acid, acetonebisulfite, amines such as ethanolamine, glycolic acid, glyoxylic acidhydrate, lactic acid, glyceric acid, malic acid, tartaric acid and saltsof the preceding acids may be used. Redox reaction catalyzing metalsalts of iron, copper, manganese, silver, platinum, vanadium, nickel,chromium, palladium, or cobalt may be used. However, after 90-99.7%,preferably 95-99.7%, of the monomers by weight, based on the totalweight of the polymer, have been converted to polymer, at least half ofthe remaining monomer is converted to polymer in the presence of0.1-1.0%, by weight based on the total weight of the polymer, of t-amylhydroperoxide. This part of the reaction may be effected as soon as90-99.7%, preferably 95-99.7%, conversion of the monomers to polymer iscompleted in the same reaction vessel or kettle. It may be effectedafter a period of time, in a different reaction vessel or kettle, or ata different temperature than the preceding part of the polymerization.Preferred is the presence of t-amyl hydroperoxide only after 90%, morepreferably after 95%, conversion of the monomers to polymer iscompleted.

[0016] Chain transfer agents such as, for example, halogen compoundssuch as tetrabromomethane; allyl compounds; or mercaptans such as alkylthioglycolates, alkyl mercaptoalkanoates, and C₄-C₂₂ linear or branchedalkyl mercaptans may be used to lower the molecular weight of the formedpolymer and/or to provide a different molecular weight distribution thanwould otherwise have been obtained with any free-radical-generatinginitiator(s). Linear or branched C₄-C₂₂ alkyl mercaptans such asn-dodecyl mercaptan and t-dodecyl mercaptan are preferred. Chaintransfer agent(s) may be added in one or more additions or continuously,linearly or not, over most or all of the entire reaction period orduring limited portion(s) of the reaction period such as, for example,in the kettle charge and in the reduction of residual monomer stage.

[0017] The average particle diameter of the emulsion-polymerized polymerparticles is preferred to be from 30 nanometers to 500 nanometers, asmeasured by a BI-90 Particle Sizer.

[0018] The aqueous composition is prepared by techniques which are wellknown in the coatings art. First, if the elastomeric coating, caulk,sealant or pressure sensitive adhesive composition is to be pigmented,at least one pigment is well dispersed in an aqueous medium under highshear such as is afforded by a COWLES® mixer or, for more viscouscompositions such as caulks and sealants, a high intensity mixer ormill. Then the waterborne polymer is added under lower shear stirringalong with other elastomeric coating, caulk, sealant or pressuresensitive adhesive adjuvants as desired. Alternatively, the aqueousemulsion polymer may be included in the pigment dispersion step. Theaqueous composition may contain conventional elastomeric coating, caulk,sealant or pressure sensitive adhesive adjuvants such as, for example,tackifiers, pigments, emulsifiers, coalescing agents, buffers,neutralizers, thickeners or rheology modifiers, humectants, wettingagents, biocides, plasticizers, antifoaming agents, colorants, waxes,and anti-oxidants.

[0019] The solids content of the aqueous coating composition may be fromabout 10% to about 85% by volume. The viscosity of the aqueouscomposition may be from 0.05 to 2000 Pa.s (50 cps to 2,000,000 cps), asmeasured using a Brookfield viscometer; the viscosities appropriate fordifferent end uses and application methods vary considerably.

[0020] The aqueous composition may applied by conventional applicationmethods such as, for example, brushing and spraying methods such as, forexample, roll coating, doctor-blade application, printing methods,air-atomized spray, air-assisted spray, airless spray, high volume lowpressure spray, air-assisted airless spray, caulk guns, and trowels.

[0021] The aqueous composition may be applied to a substrate such as,for example, plastic including sheets and films, wood, metal, previouslypainted surfaces, cementitious substrates, asphaltic substrates or thelike, with or without a prior substrate treatment such as an acid etchor corona discharge or a primer.

[0022] The aqueous composition coated on the substrate is typicallydried, or allowed to dry, at a temperature from 20° C. to 95° C.

[0023] The following examples are presented to illustrate the inventionand the results obtained by the test procedures.

[0024] Abbreviations

[0025] AA=acrylic acid

[0026] BA=butyl acrylate

[0027] MMA=methyl methacrylate

[0028] AN=acrylonitrile

[0029] EHA=2-ethylhexyl acrylate

[0030] DI water=deionized water

EXAMPLE 1 and COMPARATIVE EXAMPLE A

[0031] Preparation of predominantly acrylic emulsion polymers.

[0032] Polymerization was carried out in a 3 liter, four-neck, roundbottom glass flask equipped with a mechanical blade stirrer, athermocouple to monitor temperature, a reflux condenser, a means to heatand cool, and a nitrogen atmosphere. The flask was charged with 400 g DIwater and heated to 83° C. A monomer pre-emulsion was prepared from 280g DI water, 11 g sodium dodecylbenzene sulfonate (23% aqueous solution),885 g BA, 100 g MMA and 15 g AA. The reaction flask was charged with 4 gof ammonium persulfate dissolved in 20 g DI water and 16 g (solidsbasis) of a 100 nm seed latex with a total of 29 g of DI water. Theremaining pre-emulsion and 1.5 g ammonium persulfate dissolved in 45 gDI water were added over three hours. Heating and cooling were appliedas necessary to maintain the reaction temperature at 83 ° C. When theadditions were complete, 30 g DI water was used to rinse thepre-emulsion container into the flask. After 30 minutes, the flask wascooled to 60° C. A sample was taken, analyzed by gas chromatography andthe monomer conversion to polymer was found to be 99.62 wt. %. Thecontents of the reaction flask were divided equally between twothree-liter glass flasks equipped as described above. Both flasks weremaintained at 55° C.

[0033] For Example 1, 0.008 g of FeSO₄.7 H₂O dissolved in 5 g DI waterwas added, followed by 3.0 g of 85% aqueous tert-amyl hydroperoxidedissolved in 45 g DI water and 2.3 g of sodium formaldehyde sulfoxylatedissolved in 45 g DI water added drop-wise over one hour. The reactionmixture was cooled to 45° C. and the pH adjusted with 14 g of 14%aqueous ammonia. After cooling to room temperature the emulsion polymerwas filtered. The emulsion polymer of Example 1 had a solids content of49.3% by weight (wt %), particle size of 360 nm and a pH of 8.1. Monomerconversion to polymer was analyzed by gas chromatography and found to begreater than 99.99 wt %.

[0034] For Comparative Example A, 0.008 g FeSO₄.7 H₂O dissolved in 5 gDI water was added, followed by 3.0 g of 70% aqueous tert-butylhydroperoxide dissolved in 45 g DI water and 2.3 g sodium formaldehydesulfoxylate dissolved in 45 g DI water added drop-wise over one hour.The reaction mixture was cooled to 45° C. and the pH adjusted with 14 gof 14% aqueous ammonia. After cooling to room temperature the emulsionpolymer was filtered. Comparative Example had a solids content of 49.5wt %, particle size of 360 nm and pH of 8.2. Monomer conversion topolymer was analyzed by gas chromatography and found to be greater than99.99 wt %.

EXAMPLE 2 and COMPARATIVE EXAMPLE B

[0035] Preparation of predominantly acrylic emulsion polymers. Example 2and Comparative Example B were prepared in the same manner as Example 1and Comparative Example A, respectively, except that the polymercomposition was 91.5 BA/7 AN/1.5 AA, by weight. At the end of the first(common)stage of the reaction a sample was taken, analyzed by gaschromatography and the monomer conversion to polymer was found to be98.02 wt. %.

[0036] For Example 2, 0.008 g FeSO₄.7 H₂O dissolved in 5 g DI water wasadded, followed by 3.0 g 85% aqueous tert-amyl hydroperoxide dissolvedin 45 g DI water and 2.3 g sodium formaldehyde sulfoxylate dissolved in45 g DI water added drop-wise over one hour. The reaction mixture wascooled to 45° C. and the pH adjusted with 14 g of 14% aqueous ammonia.After cooling to room temperature the emulsion polymer was filtered. Theemulsion polymer of Example 2 had a solids content of 49.6 wt %,particle size of 370 nm and a pH of 8.6. Monomer conversion to polymerwas analyzed by gas chromatography and found to be greater than 99.99 wt%.

[0037] For Comparative Example B, 0.008 g FeSO₄.7 H₂O dissolved in 5 gDI water was added, followed by 3.0 g of 70% aqueous tert-butylhydroperoxide dissolved in 45 g DI water and 2.3 g sodium formaldehydesulfoxylate dissolved in 45 g DI water added drop-wise over one hour.The reaction mixture was cooled to 45° C. and the pH adjusted with 14 gof 14% aqueous ammonia. After cooling to room temperature the emulsionpolymer was filtered. Comparative Example had a solids content of 49.8wt %, particle size of 370 nm and pH of 8.1. Monomer conversion topolymer was analyzed by gas chromatography and found to be greater than99.99 wt %.

EXAMPLE 3 and COMPARATIVE EXAMPLE C

[0038] Preparation of predominantly acrylic emulsion polymers.Comparative Example C was synthesized via the following method: To anempty reactor was added 389.75 g DI water, 8.30 g polymeric seed, and4.00 g ferrous sulfate (0.15% aqueous), and 3.71 gtert-butylhydroperoxide (70% aqueous) with 52.00 g DI water. A monomeremulsion containing 120.00 g DI water, 36.90 g SodiumDodecylbenzenesulfonate surfactant, 552.00 g BA, 187.50 g EHA, and 10.50g AA was formed. The reactor contents were heated to 65° C. prior toaddition of the oxidant solution. The monomer emulsion was fed into thekettle simultaneously with a separate reductant solution consisting of2.22 g Sodium sulfoxylate formaldehyde in 52.00 g DI water such that atemperature of 65° C. was maintained by the polymerization and theapplication of external heat. Upon completion of the monomer emulsionand initiator feeds conversion of monomer to polymer was 95.5% byweight. Then a redox chaser system consisting of 3.71 gtert-butylhydroperoxide (70% aqueous) dissolved in 52.00 g DI water and2.22 g Sodium sulfoxylate formaldehyde in 52.00 g DI water was prepared.The oxidant solution was added all at once, and the reductant was fedinto the reactor. After the reductant addition was completed, thereactor temperature was then lowered to below 45° C. The final polymercontained 69 ppm residual monomer. The pH of the batch was raised to 7.5using ammonium hydroxide (28% aqueous) and the sample was then filteredthrough a 100 mesh screen.

[0039] Example 3 was synthesized with as was Comparative Example Cexcept that the conversion of monomer to polymer after the monomeremulsion and initiator feeds were completed was 96.3% by weight. Thechaser oxidant employed was 3.53 g t-Amylhydroperoxide (85% in t-Amylalcohol) added all at once with 52.00 g DI water. The final polymercontained 155 ppm residual monomer.

EXAMPLE 4.

[0040] Preparation of aqueous compositions and evaluation of elastomericcoatings.

[0041] Aqueous compositions were made using the following ingredients,added in the order given.: Ingredients Amount (g) Water 106.77 Tamol731¹ 12.28 Potassium tripolyphosphate 3.1 Nopco NXZ² 7.2 Acrysol RM 8W¹17.7 Propylene Glycol 20.0 Tioxide TR-92³ 100.0 Durcal 5⁴ 447.3 ButylCarbitol⁵ 13.6

[0042] The ingredients were mixed using a high shear Cowles mixer andone of the following amounts of emulsion polymer was added withstirring. Emulsion Polymer Weight (g) Example 1 502.5 ComparativeExample A 500.9 Example 2 497.4 Comparative Example B 495.5

[0043] The aqueous compositions were coated at equal volume on releasepaper at 1 mm wet thickness and dried for 23 days (at 25° C. and 50%relative humidity). Dumbbell shaped specimens having a neck width of 10mm and a neck length of 30 mm were cut out. The thickness of each samplewas measured at its neck with a micrometer. Elongation was determinedusing the Tinius Olsen UTM (Model No. H10K-S, Tinius Olsen TestingMachine Co., Inc., Willow Grove, Pa.). The controlled temperaturechamber was set at −10° C. The separation speed was set at 5.08 cm/min(2 inch/min). Elastomeric Coating containing Low Temperature EmulsionPolymer of Elongation at Break Example 1 569 Comparative Example A 416Example 2 249 Comparative Example B 235

[0044] Elastomeric coatings containing emulsion polymers Examples 1 and2 of the invention exhibit higher low temperature elongation at breakrelative to the corresponding comparative samples.

EXAMPLE 5.

[0045] Evaluation of aqueous compositions as pressure sensitiveadhesives Dried films of the emulsion polymers of Example 3 and ofComparative Example C were tested according to the following methods.Peel: PSTC-1 Peel Adhesion of Single Coated Pressure Sensitive Tapes at180° Angle (PSTC=Pressure Senstitive Tape Council, 401 N. MichiganAvenue, #00, Chicago, Ill. 60611), adhesive applied to stainless steel.Loop Tack: ASTM D6195 Standard Test Methods for Loop Tack Shear: ASTMD6463 Standard Test Methods for Time to Failure of Pressure SensitiveArticles under Sustained Shear Loading. TABLE 5.1 Evaluation of pressuresensitive adhesive properties Emulsion shear, shear loop polymer of 180peel min fail tack Example redox/chase oz/in 1″ × 1″, 1 kg mode oz Comp.C tBHP/tBHP 27.3 51 C 30.5 A 50C/50A 3 tBHP/tAHP 34.0 C  3 C 56.5 A

[0046] The pressure sensitive adhesive, dried emulsion polymer ofExample 3, of this invention exhibited improved tack relative to that ofComparative Example C.

What is claimed is:
 1. An aqueous composition suitable for use when dryas an improved elastomeric coating, caulk, sealant or pressure sensitiveadhesive comprising a predominantly acrylic aqueous emulsion polymer,said polymer having a glass transition temperature (Tg) from −90° C. to20° C., formed by the free radical polymerization of at least oneethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weightbased on the total weight of said polymer, ethylenically unsaturatedcarboxylic acid monomer until 90-99.7% of said monomers by weight, basedon the total weight of said polymer, has been converted to polymer andsubsequently at least half of the remaining monomer is converted topolymer in the presence of 0.1-1.0 wt %, by weight based on the totalweight of said polymer, t-amyl hydroperoxide.
 2. The aqueous compositionof claim 1 wherein t-amyl hydroperoxide is present only after 90% ofsaid monomers by weight, based on the total weight of said polymer, hasbeen converted to polymer.
 3. A method for preparing an aqueous emulsionpolymer suitable for use in an improved elastomeric coating, caulk,sealant or pressure sensitive adhesive comprising forming apredominantly acrylic aqueous emulsion polymer, said polymer having aglass transition temperature (Tg) from −90° C. to 20° C., by the freeradical polymerization of at least one ethylenically unsaturatednonionic acrylic monomer and 0.5-5%, by weight based on the total weightof said polymer, ethylenically unsaturated carboxylic acid monomer until90-99.7% of said monomers by weight, based on the total weight of saidpolymer, has been converted to polymer; and subsequently polymerizing atleast half of the remaining monomer to polymer in the presence of0.1-1.0%, by weight based on the total weight of said polymer, t-amylhydroperoxide.
 4. The method of claim 3 wherein t-amyl hydroperoxide ispresent only after 90% of said monomers by weight, based on the totalweight of said polymer, has been converted to polymer.
 5. A method forcoating a substrate with an aqueous composition to provide anelastomeric coating on a substrate comprising: forming said aqueouscomposition comprising a predominantly acrylic aqueous emulsion polymer,said polymer having a glass transition temperature (Tg) from −40° C. to20° C., formed by the free radical polymerization of at least oneethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weightbased on the total weight of said polymer, ethylenically unsaturatedcarboxylic acid monomer until 90-99.7% of said monomers by weight, basedon the total weight of said polymer, has been converted to polymer, andsubsequently polymerizing at least half of the remaining monomer topolymer in the presence of 0.1-1.0%, by weight based on the total weightof said polymer, t-amyl hydroperoxide; applying said aqueous compositionto said substrate; and drying, or allowing to dry, said aqueouscomposition.
 6. The method of claim 5 wherein t-amyl hydroperoxide ispresent only after 90% of said monomers by weight, based on the totalweight of said polymer, has been converted to polymer.
 7. A method forapplying an aqueous caulk or sealant composition to a substratecomprising: forming said aqueous composition comprising a predominantlyacrylic aqueous emulsion polymer, said polymer having a glass transitiontemperature (Tg) from −60° C. to 20° C., formed by the free radicalpolymerization of at least one ethylenically unsaturated nonionicacrylic monomer and 0.5-5%, by weight based on the total weight of saidpolymer, ethylenically unsaturated carboxylic acid monomer until90-99.7% of said monomers by weight, based on the total weight of saidpolymer, has been converted to polymer, and subsequently polymerizing atleast half of the remaining monomer to polymer in the presence of0.1-1.0%, by weight based on the total weight of said polymer, t-amylhydroperoxide; applying said aqueous composition to said substrate; anddrying, or allowing to dry, said aqueous composition.
 8. The method ofclaim 5 wherein t-amyl hydroperoxide is present only after 90% of saidmonomers by weight, based on the total weight of said polymer, has beenconverted to polymer.
 9. A method for providing a pressure sensitiveadhesive on a substrate comprising: forming said aqueous compositioncomprising a predominantly acrylic aqueous emulsion polymer, saidpolymer having a glass transition temperature (Tg) from −90° C. to 0°C., formed by the free radical polymerization of at least oneethylenically unsaturated nonionic acrylic monomer and 0.5-5%, by weightbased on the total weight of said polymer, ethylenically unsaturatedcarboxylic acid monomer until 90-99.7% of said monomers by weight, basedon the total weight of said polymer, has been converted to polymer, andsubsequently polymerizing at least half of the remaining monomer topolymer in the presence of 0.1-1.0%, by weight based on the total weightof said polymer, t-amyl hydroperoxide; applying said aqueous compositionto said substrate; and drying, or allowing to dry, said aqueouscomposition.
 10. The method of claim 5 wherein t-amyl hydroperoxide ispresent only after 90% of said monomers by weight, based on the totalweight of said polymer, has been converted to polymer.